The Food Standards Agency insists there is no evidence that any contaminated vegetables have reached the UK (although the exact source of the outbreak has not yet been determined). Nevertheless, the footage of destroyed Spanish cucumbers – originally thought to be the problem – was enough to make most people cast a worried eye in the direction of their fridge.

This isn't the first time danger has lurked close to our lettuce. In 2007, an outbreak of salmonella in the UK was traced to imported basil, while an E coli outbreak in the US in 2006 was caused by pre-packed spinach. And in 2008, 145 people in the US were made ill by eating tomatoes infected with a rare strain of salmonella.

In her book Not on the Label, Guardian journalist Felicity Lawrence says that between 1992 and 2000, when bagged salads took off, nearly 6% of food-poisoning outbreaks were associated with prepared vegetables and salads. In 1996 a study of retail samples of bagged salad found 13% contained E coli.

So should we forgo our five-a-day for the sake of our health? Sadly for vegetable-hating children, the answer is no. The Health Protection Agency says that while small, localised outbreaks of E coli have been linked to fruits and vegetables, they are very rare.

Gad Frankel, professor of molecular pathogenesis at Imperial College London, says: "I don't think salads are particularly dangerous. The rate of infection is very low, so when it happens it really makes the news because it's so rare." Any increase in incidents, he says, may be due to the fact we now eat more salad as we seek to make our diets healthier.

Mark Wilcox, professor of medical microbiology at the University of Leeds, agrees, saying that while salads have more potential for passing on deadly organisms because they are uncooked, "they are not a high risk or you would hear about it all the time."

Bagged salad, he says, which is often washed in spring water or chlorine, is less likely to be infected than a whole lettuce where the heart is harder to clean. E Coli is found on the surface of vegetables, adds Wilcox, because it is a faecal organism so gets on to them from the soil, water or people's hands – and other infections can also be caused in this way. "Bean sprouts are occasionally contaminated with salmonella – again from faecal matter. Listeria is an organism that can be soil-borne and get on to vegetables too and the other one I always remember is toxaplasma – excreted by kittens."

Stephen Vaughan, whose company All Food Hygiene has run food hygiene courses in the UK for 20 years, is less optimistic. "In the last decade there has been a rise in low-dosage organisms such as E coli, campylobacter and listeria. With salmonella, you need to eat millions of the bacteria to get ill, but with campylobacter you need only 500. Campylobacter is the number one cause of food poisoning in the UK.

"We have to be much more careful because we are importing so much more salad and vegetables from abroad. In the UK we have got rid of sewage in our rivers and our water is cleaner."

While the experts say there is no need to worry, the FSA is advising people to wash vegetables that cannot be peeled or cooked. But is a quick splash enough? "The more you wash and soak, the greater the effect," says Wilcox. "When I was a kid, my gran would always soak the salad in salty water as it is somewhat antibacterial."

Vaughan is more cautious. "The most sensible way to wash vegetables at home is to use Milton Sterilising Fluid. You need to use a double sink method – one bowl with Milton diluted in water (as per the instructions), then put your fruit and vegetables in there for 20 minutes. Fill the other sink with tap water to wash off the chlorine. It leaves no taste and kills the bacteria."

If all this is putting you off, Frankel says, comfortingly: "I will still have a salad today, and so will my children."